Approaches to validation
Two basic approaches to validation —
First is based on evidence obtained through testing (prospective and concurrent validation), and
Second is based on the analysis of accumulated (historical) data (retrospective validation).
Whenever possible, prospective validation is preferred. Retrospective validation is no longer Used Nowadays.
Both prospective and concurrent validation, may include:
• Extensive product testing, which may involve extensive sample testing (with the estimation of confidence limits for individual results) and the demonstration of intra- and inter-batch homogeneity;
• simulation process trials;
• challenge/worst case tests, which determine the robustness of the process;
• control of process parameters being monitored during normal production runs to obtain additional information on the reliability of the process.
Scope of validation:
An appropriate and sufficient system including organizational structure and documentation infrastructure, sufficient personnel and financial resources to perform validation tasks in a timely manner. Management and persons responsible for quality assurance should be involved.
Personnel with appropriate qualifications and experience should be responsible for performing validation. They should represent different departments depending on the validation work to be performed.
Validation should be performed in a structured way according to the documented procedures and protocols.
Validation should be performed:
— for new premises, equipment, utilities and systems, and processes and procedures;
— at periodic intervals; and
— when major changes have been made.
(Periodic re-validation or periodic re-qualification may be substituted, where appropriate, with periodic evaluation of data and information to establish whether re-qualification or re-validation is required.)
Validation should be performed in accordance with written protocols.
A written report on the outcome of the validation should be produced.
Validation should be done over a period of time, e.g. at least three consecutive batches (full production scale) should be validated, to demonstrate consistency. Worst case situations should be considered.
There should be a clear distinction between in-process controls and validation. In-process tests are performed during the manufacture of each batch according to specifications and methods devised during the development phase. Their objective is to monitor the process continuously.
When a new manufacturing formula or method is adopted, steps should be taken to demonstrate its suitability for routine processing. The defined process, using the materials and equipment specified, should be shown to result in the consistent yield of a product of the required quality.
Manufacturers should identify what validation work is needed to prove that critical aspects of their operations are appropriately controlled. Significant changes to the facilities or the equipment, and processes that may affect the quality of the product should be validated. A risk assessment approach should be used to determine the scope and extent of validation required.
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Reference: WHO Technical Report Series, No. 937, 2006